Vehicle position marking device

ABSTRACT

A wheeled device adapted for attachment to a vehicle for marking the location on a surface where the vehicle traveling over the surface attains a selected speed. The device includes a marking gun adapted to fire an electrically detonable cartridge containing a color marking substance and an electronic speedometer that electrically detonates the cartridge at the selected speed, thereby discharging the color marking substance downwardly against the surface to mark thereon the location where the vehicle attains the selected speed.

United States atent Jamison et al.

[ July 4, 1972 [54] VEHICLE POSITION MARKING DEVICE [72] Inventors:Robert W. Jamison, Springfield Township,

Delaware County, Pa.; Paul A. Norcross, Downers Grove, Ill.

[73] Assignce: Union Oil Company of California, Los Angeles, Calif.

[22] Filed: June 15, 1970 [21] Appl.N0.: 46,181

51 1m. (:1 ..G01p3/52,G0lc 22 02 [58] Field of Search ..340/62; 73/128,129, 488,490; 74 3; 116/37; 317 5; 42/84; 324/163, 175, 166, 180

[56] References Cited UNITED STATES PATENTS 3/1964 Davies ..73/4882,279,409 4/l942 Milster et al ..73/l28 3,231,807 l/l966 Willis...324/l75 3,332,406 7/l967 Perry et al. ..3 1 7/5 PrimaryExaminer-Thomas B. Habecker Assistant Examiner-Glen R. Swann, III

Attorney-Milton W. Lee, Richard C. Hartman, Lannas S. Henderson, DeanSandford and Robert E. Strauss 57 1 ABSTRACT A wheeled device adaptedfor attachment to a vehicle for marking the location on a surface wherethe vehicle traveling over the surface attains a selected speed. Thedevice includes a marking gun adapted to tire an electrically detonablecar tn'dgc containing a color marking substance and an electronicspeedometer that electrically detonates the cartridge at the selectedspeed, thereby discharging the color marking substance downwardlyagainst the surface to mark thereon the location where the vehicleattains the selected speed.

10 Claims, 10 Drawing Figures Patented July 4, 1972 3,675,19

3 Sheets-Sheet 2 INVENTORS #03577 W. 44/14/50 A404 4. A/ORCAOSS.

Patented July 4, 1972 3,675,199

3 Sheets-Sheet 3 CONVERTER 0C POWER 500/9625 P404 ,4. A ORCAOSS T I I II P- b BY if, my /0 S ATTORNEY VEHICLE POSITION MARKING DEVICE Thisinvention relates to vehicle performance testing, and more particularly,to a device attachable to a vehicle for marking the location on asurface where the vehicle traveling over the surface attains a selectedspeed. The device has particular application in measuring vehiclestopping and acceleration distances.

It is often necessary to measure the distance traversed by a movingvehicle during a particular speed interval in order to obtaininformation concerning various performance capabilities of the vehicle.For example, in measuring the stopping or acceleration capability of avehicle, the distance traversed by the vehicle during a stopping test,or alternatively, during an acceleration test, must be measured. Thisinformation is of great importance to competitive automobilemanufacturers for design, promotion and advertising purposes, and isalso valuable to certain state and federal agencies which performhighway safety functions.

While the mechanics of measuring distance may be relatively simple, itis sometimes very difficult to accurately establish the points betweenwhich the measurement is to be made. For example, in determining thevehicle stopping distance, the minimum longitudinal distance required tobring the vehicle traveling at a standard speed to a complete halt ismeasured This minimum distance is the distance traversed by the vehicleduring deceleration from a standard test speed to a complete halt, anddoes not include any distance traversed prior to deceleration to thestandard test speed or after the vehicle is initially brought to a halt.Hence, the exact location of the vehicle at the commencement andtermination of the test must be accurately determined. The location ofthe halted vehicle at the termination of the stopping phase is easilydetermined, and thus the only major difficulty in measuring the stoppingdistance is in accurately establishing the location of the vehicle atthe commencement of the stopping phase, i.e., the location where thevehicle decelerates through the standard test speed. A similar problemis encountered in determining the distance required for a vehicle toaccelerate from zero to a standard test speed or between two standardtest speeds. In this test, the major difficulty is determining thelocation of the vehicle at the termination of the acceleration phase,i.e., the location where the vehicle accelerates through the standardspeed, or, in the case where the acceleration test is started at otherthan a zero initial speed, in determining the locations where thevehicle passes through the initial and terminal standard test speeds.Accordingly, the exact location where the vehicle attains a standardtest speed must be determined in both the stopping and accelerationtests.

Several devices for marking the location where a vehicle attains apreselected speed have heretofore been proposed. One such device employsa manually fired marking gun that propels a color marking substance ontothe surface over which the vehicle is traveling so as to produce areadily visable spot on the surface. The gun is fired by a compressiondetonable cylinder actuated by a solenoid that can be energized from thedrivers compartment. In a typical application, a vehicle is driven overa test tract at a speed greater than or equal to the standard orpre-selected speed. The driver applies the vehicle brakes and, as thevehicle decelerates through the standard speed, the marking gun ismanually fired to mark the location where the standard speed isattained. When the vehicle finally comes to a halt, the distance betweenthe marked spot on the test track and the halted vehicle is measured toobtain the stopping distance.

The accuracy of the measurements obtained by this technique is dependentupon several factors which can vary from test to test. For example,error can be introduced into the measured distance by inaccuracies inthe speedometer, by a different response time in triggering the markinggun for comparable tests, by a triggering lag time in the marking gun,and by a detonation lag time in the firing of the marking cartridge.Often, particularly when difierent drivers are used in the tests, themeasured stopping distances or acceleration distances are grosslyinaccurate. For example, in measuring the stopping distance of a vehicletraveling at a standard test speed of 65 miles per hour, the abovedescribed procedure has resulted in errors as great as percent of thetrue stopping distance. Accordingly, need exists for an improved devicethat accurately marks the location where a vehicle attains a selectedspeed, that does not require manual operation, that is relatively simpleand economical to construct, and that is relatively compact and easy tooperate.

Accordingly, a principal object of this invention is to provide a devicefor marking the location on a surface where a vehicle traveling over thesurface attains a selected speed. Another object of the invention is toprovide a device for marking the location where a decelerating vehicleattains a selected speed. Still another object of the invention is toprovide a device for marking the location where an accelerating vehicleattains a selected speed. A further object of the invention is toprovide an improved marking device for marking on a surface the locationof a vehicle traveling over the surface. A still further object of theinvention is to provide an improved electrically detonable markingcartridge.

Other and related objects will become apparent from the followingdescription and attendant drawings, wherein like numerals refer tocorresponding parts, and in which:

FIG. 1 is an elevation view showing the device of this inventionattached to the rear of a test vehicle;

FIG. 2 is a partial longitudinal cross-sectional view of the devicetaken along the line 2-2 in FIG. 1;

FIG. 3 is a cross-sectional view of another embodiment of pulsegenerator;

FIG. 4 is an elevation view of the perforated disc employed in the pulsegenerator illustrated in FIG. 3;

FIG. 5 is a longitudinal cross-sectional view illustrating the markinggun of this invention;

FIG. 6 is a cross-sectional view of the marking gun taken along the line6-6 in FIG. 5;

FIG. 7 is a longitudinal cross-sectional view illustrating the markingcartridge of this invention;

FIG. 8 is a block diagram illustrating the electrical circuitry employedin this invention;

FIG. 9 is a schematic electrical diagram illustrating the electricalcircuitry of the voltage comparator of this invention; and

FIG. 10 is a schematic electrical diagram illustrating the detonatingcircuit of this invention.

The foregoing objects and their attendant advantages can be realizedwith a wheeled device adapted for attachment to a vehicle, and whichincludes a marking gun adapted to fire an electrically detonablecartridge containing a color marking substance and an electronicspeedometer that electrically detonates the cartridge at a selectedspeed, thereby discharging the color marking substance downwardlyagainst the surface over which the vehicle is traveling to mark thereonthe location where the vehicle attains the selected speed. Theelectronic speedometer is comprised of a wheel mounted on a frame andadapted for rolling contact with said surface, and means forelectronically measuring the speed of rotation of said wheel, the speedof rotation of the wheel being proportional to the linear velocity ofthe vehicle.

Referring now to FIGS. 1 and 2 of the drawings, the numeral 10 generallyrepresents the wheeleddevice of this invention adapted for connection tothe rear bumper 12 of test vehicle 14 which is illustrated travelingover surface 16. Device 10 is comprised of frame 20 having axle 22mounted transversely at one end thereof, wheel 24 being rotatablymounted on axle 22 and in rolling contact with surface 16, marking gun26 in a downwardly directed vertical position on frame 20, and hitch 28which permits the device to be readily connected and disconnected fromvehicle 14. Hitch 28 is provided with spring 30 which maintains adownward force on the device so that wheel 24 is firmly maintained incontact with surface 16. Marking gun 26 is adapted to receive anelectrically detonable cartridge containing a color marking substancewhich, when detonated, is discharged downwardly against surface 16marking the location of the vehicle at that particular instant.Alternatively, marking gun 26 can be mounted directly on vehicle 14.

The speed of vehicle 14 is determined by electronically detecting thespeed of rotation of wheel 24, which velocity is proportional to thelinear velocity of the vehicle. The rotational speed of wheel 24 isdetected by generating a series of electrical pulses having a frequencyproportional to the rotational velocity of the wheel, and convertingthese pulsed signals to an analog electrical signal having a voltageproportional to the rotational speed of wheel 24. The pulsed signals aregenerated by passing a light beam through a series of light perviousareas that rotate with wheel 24, the incident light activating aphotoelectric cell that produces a pulsed signal having a frequencyproportional to the speed of rotation of the wheel.

In one embodiment of the invention, opaque disc 32 is attached to wheel24 so that it revolves with the wheel. Disc 32 is provided with aplurality of light pervious areas 34 of substantially uniform size andshape evenly disposed about its periphery and substantially equidistantfrom the axis of wheel 24. Light pervious areas 34 can be formed bydrilling small apertures through an opaque metallic or plastic disc;however, it is preferred that the precisely spaced and minute lightpervious areas be obtained by photographic techniques. These techniquesare well known in the art and briefly comprise treating the disc with aphotographic coating, exposing various areas of the disc to light, andchemically treating the coating to produce a plurality of light perviousareas evenly spaced on the otherwise opaque material.

As particularly illustrated in FIG. 2, a light source 36 is mounted onframe 20 adjacent to disc 32 so that light from the light source passesthrough the light pervious areas 34 and impinges on photoelectric cell38 mounted on frame 20 on the opposite side of disc 32 from the lightsource. Light source 36 and photoelectric cell 38 are connected to asuitable power source and to the electronic speedometer circuitry, whichis in part contained within the control box 40 mounted on frame 20, bymeans of suitable electrical conductors, not shown. As the vehicletravels over the surface, wheel 24 rotates about axle 22 causing thelight pervious areas 34 in disc 32 to successively pass between lightsource 36 and photoelectric cell 38. Thus, light from light source 36intermittently strikes photoelectric cell 38 causing the photoelectriccell to generate a series of electrical impulses. Accordingly, as wheel24 rolls along the surface, a series of electrical impulses are producedby the photoelectric cell, the frequency of the pulses beingproportional to the speed of rotation of wheel 24, which is in turnproportional to the linear velocity to vehicle 14.

In another and preferred embodiment of the invention, the pulsegenerating device is a separate unit mounted on axle 22 so as to projectoutwardly at one side of wheel 24. This embodiment of pulse generatingdevice is particularly illustrated in FIGS. 3 and 4, wherein opaque disc50 having a plurality of perforations 52 of uniform size and shapeevenly disposed about its periphery is depicted rotatably mounted inhousing 54, which is comprised of a support plate 56 and a mating coverplate 58 secured thereto by bolts 60. Both support plate 56 and coverplate 58 are apertured to accommodate shaft 62, which is rotatablysupported within housing 54 by bearings 64 and 66. Disc 50 is attachedto radially extending flange 68 of shaft 62 by bolts 70. Flanged bushing72 is mounted in the aperture in support plate 56 and securedtherewithin by means of pin 74. Shaft 62 is provided with key 76adjacent to its inboard end which is adapted to engage a keyway in axle22, not shown. The outboard end of shaft 62 can be provided with asimilar keyway 78 for attaching another device, such as tachometer, orthe like. The pulse generating device is mounted on axle 22 by nut 80,which threadably engages the axle. Shaft 62 is axially aligned with andkeyed to axle 22 so that disc 50 is rotably driven at the same angularvelocity as wheel 24.

Light source 82 is mounted in housing 54 by means of threaded bushing84, and is positioned adjacent to disc 50 so that light from the lightsource passes through perforations 52 and impinges on photoelectric cell86. The photoelectric cell is mounted within housing 54 by means ofthreaded bushing 87, so that the photoelectric cell is adjacent toperforations 52 and on the opposite side of disc 50 from the lightsource. Light source 82 and photoelectric cell 86 are respectivelyconnected to the electrical circuitry by means of conductors 88, 90, 92and 94. The electrical components are protected from dust and moistureby a sealed cover 96. Exterior of the pulse generator, the conductorscan be enclosed within a flexible conduit, not shown, connected toaperture 98 in cover 96. This embodiment of the pulse generating unitoperates similarly to the wheel mounted unit, with light from the lightsource passing through the perforations in disc 50 and activating thephotocell to produce a series of electrical pulses having a frequencyproportional to the angular velocity of wheel 24, which in turn isproportional to the linear velocity of vehicle 14.

One embodiment of marking gun 26 useful in the practice of thisinvention is shown in FIGS. 5 and 6. The illustrated device includes aframe 100 having an integrally formed pivot pin 102 at its forward endand an integral breech block 104 at an intermediate location, the framedefining a hollow forward cavity 106 and a hollow butt cavity 108interconnected through aperture 110 located immediately below breechblock 104. A short barrel 112 having an integral chamber 1 14 adapted toreceive an electrically detonable cartridge 170 and an integrally formedrectangular base 116 is pivotly mounted on pivot pin 102. Forward cavity106 is adapted to receive base 116 and the chamber end of barrel 112,chamber 114 being closed by abutment with breech block 104. Barrel 1 12,by virtue of its pivotal attachment to frame 100, can be moved from theopen position illustrated in FIG. 5, providing access to chamber 114, toa closed firing position in which the chamber end of barrel 1 12 abutsthe breech block.

Barrel 112 is maintained in a closed position by means of releasablelocking mechanism 120 mounted in butt cavity 108 of frame 100. Thelocking mechanism is comprised of locking arm 122 and release arm 124pivotly mounted on the interior of frame 100 by means of pins 126 and128, respectively. Arm 122 is mounted so that one end projects throughaperture 1 10 and engages notch 130 at the rear of base 116. Locking arm122 is held in engagement with notch 130 by spring 132 which biases thelocking arm against base 116. The other end of locking arm 122 isprovided withgear teeth 134 which mate with similar gear teeth 136 onone end of release arm 124. The other end of arm 124 projects outwardlyfrom the frame and terminates in a tab or button 158 which may beoperated to release the locking mechanism, allowing the barrel to bemoved to an open position. A downward force applied to release button158 causes release arm 124 to pivot clockwise about pin 128, which inturn overcomes the biasing force of spring 132 and causes locking arm122 to be moved in the opposite direction, thereby withdrawing arm 122from engagement with notch 130. Upon release of the force applied torelease button 158, the biasing force returns the arms 122 and 124 totheir original positions.

An L-shaped mounting bracket 140 is bolted to the butt of frame 100 bybolt 142 to provide means for attaching marking gun 26 to frame 20 ofthe wheeled device. Bracket 140 is provided with an elongated slot 144through which the marking gun is adjustably bolted to frame 20 so thatthe marking gun is supported in a substantially vertical, downwardlydirected position when wheeled device 10 is attached to the vehicle 14,with the munle end of the gun being maintained a short distance abovesurface 16. Bracket 140 is apertured at 146 and 148 and two-poleelectrical terminals 150 and 152 inserted through these apertures,respectively, and electrically insulated from the bracket. Theelectrical firing mechanism, which will hereinafter be more fullydescribed, is electrically connected through conductors 154 and 156 toone pole of each of the terminals 150 and 152, respectively, andelectrically detonable cartridge is electrically connected to the otherpoles of terminals 150 and 152 through conductors 172 and 174,respectively. The gun is loaded by inserting cartridge 170 into chamber114, moving the barrel to the closed position, and connecting conductors172 and 174 to the terminals. Breech block 104 is provided withlongitudinal slot 138 to accommodate conductors 170 and 172 when barrel112 is in closed position.

Marking gun 26 can be conveniently constructed from a conventional shotgun, such as a single-shot breech loading shot gun in 8, 10, 12, 16 or.410 gauge. Also, it should be recognized that two or more of themarking guns can be mounted on wheeled device to provide marks onsurface 16 responsive to different signals, or that a double barrel guncan be employed to provide this feature.

As illustrated in F IG. 7, electrically detonable cartridge 170 iscomprised of tubular casing 176 attached to flanged base 178. Thecartridge is loaded with capsule 180 of a color marking substance, suchas thick paint, and an electrically detonable primer 182 electricallyconnected to conductors 172 and 174, which pass through aperture 184 inbase 178. To minimize time lag in the firing system, it is preferredthat primer 182 have a detonation time below about 30 milliseconds, andmore preferably below about milliseconds. On detonation, primer 182propels the capsule of color marking substance from cartridge 170. Thecolor marking substance passes through barrel 112 and strikes surface16, leaving thereon a clear mark of colored substance showing thelocation of the device on the surface at the time of detonation.Cartridge 170 can be readily constructed from a conventional shot gunshell of a size adapted to fit chamber 114 by removing the wadding, shotand primer, and inserting therein an electrically detonable primer. 182and capsule 180. Also, it is apparent that cartridge 170 can beconveniently constructed from an empty shell or from the component partsthereof.

The schematic arrangement of the electronic speed measuring anddetonating circuits is illustrated in FIG. 8. Photoelec' tric cell 38 iselectrically connected to pulse conditioner 200 by conductor 202. Pulseconditioner 200 receives the electrical impulses from the photoelectriccell and produces modulated impulses having uniform amplitude and waveform. The number and frequency of the modulated impulses is equal to thenumber and frequency of impulses produced by the photoelectric cell,however, it is recognized that in other embodiments of this mechanismthe number and/or frequency of the modulated impulses can beproportionally higher or lower than the input impulses. While manyconventional conditioner circuits can be employed in the practice ofthis invention, a preferred circuit comprises a solid state one-shotmultivibrator, an electronic filter and an amplifier in seriesconnection.

The output of pulse conditioner 200 is electrically connected byconductor 204 to pulse rate converter 206 and, through switching circuit210 and conductor 212, to pulse counter 214. Pulse rate converter 206 isa digital-analog device that converts the modulated impulses from thepulse rate conditioner to an analog electrical signal proportional tothe frequency of the modulated pulses. While the analog electricalsignal can be varied in different ways to represent the frequency of thepulsed signal, i.e., by varying the current, the frequency, or thephase, it is preferred that the analog output from pulse rate converter206 be a relatively stable DC potential having a voltage directlyproportional to the rate at which the modulated impulses are received,i.e., the number of impulses received per unit of time. By relativelystable it is meant that the output signal is substantiallynon-oscillating for a fixed impulse rate. While it is desired that theanalog output of the pulse rate converter be completely stable, it isrecognized that minor voltage oscillations can occur, and it ispreferred that the converter circuit be selected so that the amplitudeof each of the oscillations is below about 1 percent of the total outputpotential. Conventional digital-analog converter circuits are well knownin the art, hence a description thereof is not presented herein.

The output of pulse rate converter 206 is electrically connected bymeans of conductor 218 to voltmeter 216 and voltage comparator 220. Theanalog DC output potential from the pulse rate converter is continuouslymonitored by means of the voltmeter. Since the analog output from pulserate converter 206 is proportional to the vehicle speed, voltmeter 216can be calibrated directly in units of vehicle speed. Thus, voltmeter216 can be employed as an electronic speedometer which can be used toaccurately determine the instantaneous speed of the vehicle at anyinstant of time. Voltage comparator 220 compares the magnitude of theanalog DC potential output from the pulse rate converter with areference DC- potential corresponding to a reference vehicle speed, andproduces an electrical output signal when the analog signal is equal toor less than the reference potential. Since the analog potential isrepresentative of vehicle speed, the comparator produces an electricalsignal whenever the vehicle is traveling at a speed equal to or lessthan the reference speed.

The output of voltage comparator 220 is electrically connected by meansof conductor 222 to switching circuit 210 and detonating circuit 224.Switching circuit 210 comprises two electrically activated switchesconnected in series. While coil operated relays can be employed, it ispreferred that solid state switches such as silicon controlledrectifiers be used. One of the switches is activated into the conductivestate by the output signal from voltage comparator 220 when the vehicleattains a preselected or reference speed. The second switch is used inmeasuring vehicle stopping distance, and is activated into theconductive state whenever the vehicle decelerates. This switch can beconveniently connected to the vehicle brake light circuit so that it isactivated whenever the vehicle brakes are applied. Thus, when thevehicle is traveling at a speed greater than the reference speed withthe brakes off, both switches are in the non-conductive state and pulsecounter 214 is disconnected from the modulated output of pulseconditioner 200. However, when the brakes are applied, the second switchis electrically activated into the conductive state and, as the vehicledecelerates to the reference speed, the first switch is electricallyactivated into the conductive state connecting the output of the pulseconditioner to pulse counter 214. Hence, in this embodiment of thecircuitry useful in measuring vehicle stopping distance, the pulseoutput from pulse conditioner 200 is counted or totalized on pulsecounter 214 during the period that the vehicle brakes are applied andthe vehicle speed is equal to or less than the reference speed. Thetotal number of pulses during this period is an indication of thedistance traveled during the stopping test. Various conventionaltotalizers or pulse counters are commercially available, and hence adetailed description of an exemplary totalizer circuit is unnecessary.While pulse counter 214 can employ any means of recording and/orindicating the accumulated number of pulses, it is preferred that theaccumulated number of pulses be indicated on nixi-tubes for visualobservation by the vehicle driver.

Detonating circuit 224 is electrically connected to marking device 26 byconductors 154 and 156. This circuit, responsive to the output signalfrom voltage comparator 220, generates the firing signal that detonatesthe electrically detonable primer in cartridge causing the color markingsubstance to be discharged.

While several embodiments of voltage comparator circuits can beemployed, one preferred embodiment utilizing solid state circuitry isillustrated schemetically in FIG. 9. The illustrated circuit comprisestwo differential amplifiers coupled together with a constant currentgenerator. The collectors of NPN transistors T and T in the firstdifferential amplifier are respectively connected to the bases of PNPtransistors T and T in the second difierential amplifier. The emittersof transistors T and T are commonly connected to the collector of NPNtransistor T in the constant current generator. A DC power supply isconnected across positive terminal 240 and negative terminal 242.Positive terminal 240 is connected through resistor R to the base oftransistor T and the collector of transistor T1; through resistor R tothe base of transistor T and the collector of transistor T2; throughresistor R to the emitters of transistors T and T4; through variableresistor R to the emitter of PN P transistor'li, and to a normallyclosed contact in relay 8,; through resistor R and potentiometer R tothe base of transistor T and through resistor R potentiometer R, andresistor R to the base of transistor T Negative terminal 242 isconnected through resistor R to the collector of transistor T throughresistor R to the collector of transistor T and the base of transistor Tthrough diode D to the collector of transistor T and to the positiveterminal of the coil in relay 8,; to the negative terminal of the coilin relay 8,; through resistor R to the base of transistor T and throughresistor R to the emitter of transistor T The analog DC potential frompulse rate converter 206 is connected to the base of transistor T,through terminal 244, and output conductor 222 is connected to terminal246; In operation, a DC potential is applied across terminals 240 and242 of the comparator circuit. The current flowing into the amplifiercircuit is divided between the first and second differential amplifiers,with the total current through the first differential amplifier beingcontrolled by the constant current generator. Potentiometer R isadjusted so that a reference DC potential corresponding to a referencevehicle speed is impressed across the base of transistor T The analog DCpotential from pulse rate converter 206 is applied to the base oftransistor T,. When the analog DC potential is greater than the Ireference potential, transistor T conducts more current than transistorT and causes the collector of transistor T to become more negative thanthe collector of transistor T Hence transistor T conducts sufficientcurrent to energize relay switch S which interrupts the output signal.Conversely, when the analog DC potential is less than the referencepotential, the opposite effect occurs, i.e., transistor T does notconduct sufficient current to maintain relay switch S energized, thusallowing current to flow through output terminal 246.

FIG. 10 illustrates one embodiment of a detonating circuit that can beemployed in the practice of this invention. As shown in the diagram, DCpower source P, silicon controlled rectifier S and relay S are allseries connected in closed circuit with marking device 26, with themarking device being connected through conductors 154 and 156. The gateof silicon controlled rectifier S is connected to conductor 222 and thecoil of relay 8;, is electrically connected through conductors 250 and252 to the braking system ofthe test vehicle, e.g.,

- connected to the brake light switch, so that relay 8;, is energizedwhenever the brakes are applied. Hence, a firing potential is appliedacross the marking device 10 whenever rectifier S is activated into theconductive state by the output from voltage comparator 220 and relay 8,,is energized by the application of the vehicle brakes, the firingpotential causing the detonation of the electrically detonable primer incartridge 170. When the device is employed to measure accelerationdistance, relay 8;, is deleted from the circuit or bypassed and switch Sin the comparator circuit is replaced with a normally open relay switch.In cases where the output from voltage comparator 220 is sufficient toquickly detonate the electrically detonable primer in marking device 26,the detonating circuit can be replaced by a switching circuit similar toswitching circuit 210.

The electronic speed measuring and firing circuitry must be calibratedbefore tests are conducted so as to insure accurate perfonnance of theequipment. The calibration of the circuits of this invention can beaccomplished in several ways, however, the following procedure ispreferred. A three track oscilloscope is connected to the outputterminals of the pulse conditioner, pulse rate converter and voltagecomparator. The circuits are turned on and allowed to warm up forapproximately 1 hour. The wheel is rotated so that the photoelectriccell produces a continuous source of electrical impulses, and the pulseconditioner adjusted so that the modulated impulses generated by thecircuit are of desired amplitude and shape. The wheel is then spun atvarious speeds of revolution corresponding to known vehicle speeds, andthe pulse rate converter is adjusted so that the analog potentialproduced by the circuit has a direct linear relationship with the wheelspeed. The voltage comparator is calibrated by adjusting resistors R,and R so that when measuring the stopping distances, an output signal isdetected on the oscilloscope when the wheel is spinning at a speed equalto or less than the reference speed, and when measuring the accelerationdistances an output signal is detected when the wheel is spinning at aspeed equal to or greater than the reference speed. Finally, theswitching and detonating circuits are checked by connecting the outputterminals in these circuits to the oscilloscope and rotating the wheelat a speed greater than the standard speed. The wheel is thendecelerated through the reference speed and the oscillograph observed todetermine whether or not a signal is produced in each circuit preciselyat the moment the wheel decelerates through the reference speed. If noelectrical signal is detected, or if a lag in the signal is detected,the resistors R and R in the comparator circuit are readjusted. Thisprocedure is repeated until the desired results are obtained. Inaddition to the initial calibration, it is recommended that the circuitsbe recalibrated periodically to compensate for any potential driftingwhich may occur in the various circuits during operation.

The test apparatus of this invention can be used to measure the stoppingand acceleration distances of a vehicle. In measuring the stoppingdistance, the wheel assembly and electrical circuitry are calibrated andattached to the test vehicle. The vehicle is driven over a test track ata speed equal to or greater than the reference speed, and the brakes areapplied. As the vehicle decelerates through the reference speed, thecomparator circuit generates an electrical signal which detonates themarking gun and closes the circuit between the pulse conditioner andpulse counter. With this dual switch hookup, the marking substance ispropelled downwardly against the track surface and the pulse counterbegins to receive modulated impulses from the pulse conditioner at ornear the precise moment the vehicle decelerates through the referencespeed, regardless of the speed of the vehicle at the time that thebrakes were applied. The stopping distance is the distance from themarked surface to the stopped vehicle and can be readily measured with ameasuring tape or like device. The stopping distance is also determinedby multiplying the total number of pulses counted by the pulse counterby the distance traversed by the wheel in generating one completeelectrical impulse.

In the embodiment of the device for measuring the acceleration distance,the second switch in switching circuit 210 and relay S in the detonationcircuit are deleted or bypassed, switch S in the voltage comparatorcircuit is replaced by a normally open relay switch, and the firstswitch in switching circuit 210 is replaced by a switch which isnormally conductive and is activated into the non-conductive state byelectrical exitation. The initial position of the vehicle is marked andthe vehicle is driven over the test track at maximum acceleration. Asthe vehicle accelerates through the reference speed, the comparatorcircuit generates an electrical signal which in turn detonates themarking gun and opens the circuit between the pulse conditioner andpulse counter. The marking gun propels the marking substance downwardlyagainst the track surface and the pulse counter stops counting themodulated impulses at or near the precise moment the vehicle acceleratesthrough the standard speed. The minimum acceleration distance is thedistance from the vehicle position at the start of the acceleration testto the marked point on the track surface. The acceleration distance canalso be determined by multiplying the total number of pulses counted bythe pulse counter by the distance traversed by the wheel in generatingone complete electrical impulse.

It is apparent to those skilled in the art that several modificationscan be made to the apparatus and method of this invention and such areconsidered within the scope of this invention. It is also apparent that,with the disclosed apparatus, the minimum stopping distance can besimply and accurately measured. The effect of subtle changes in thebraking system of the vehicle can be detected. The distance required fora vehicle to accelerate from zero or a given speed to a standard speedcan be accurately measured. Also the instantaneous position of a movingvehicle can be marked. Hence, this invention represents a substantialadvancement over the prior art devices for marking the location where avehicle attains a preselected speed.

The invention having thus been described, we claim:

1. A device for marking on a surface the location where a vehicletraveling over the surface attains a selected speed, which comprises:

speedometer means adapted for attachment to said vehicle for generatingan electrical signal proportional to the speed of said vehicle;

a gun adapted to fire an electrically detonable cartridge containing acolor marking substance, said gun being adapted for mounting in avertical, downwardly directed position above said surface; and

means electrically connected to said cartridge for detonating saidcartridge when the generated electrical signal attains a valuecorresponding to the selected speed;

whereby, upon detonation of the cartridge, the color marking substanceis propelled downwardly against said surface to mark thereon thelocation that the vehicle attains the selected speed.

2. The device defined in claim 1 wherein the electrical signal generatedby said speedometer means is a relatively non-oscillating DC potentialhaving a voltage proportional to the speed of the vehicle.

3. A device for marking on a surface the location where a vehicletraveling over the surface attains a selected speed, which comprises:

a frame adapted for detachable connection to said vehicle;

a wheel rotatably mounted on said frame and adapted for rolling contactwith said surface;

speedometer means for generating an electrical signal proportional tothe speed of revolution of said wheel;

a gun adapted to fire an electrically detonable cartridge containing acolor marking substance, said gun being mounted in a vertical,downwardly directed position on said frame; and

means electrically connected to said cartridge for detonating saidcartridge when the generated electrical signal attains a valuecorresponding to the selected speed.

4. A device for marking on a surface the location where a vehicletraveling over the surface attains a selected speed, which comprises:

speedometer means adapted for attachment to said vehicle for generatinga series of electrical pulses having a frequency proportional to thespeed of said vehicle;

conditioner means electrically connected to said speedometer means formodulating said electrical pulses so as to produce a series of modulatedelectrical pulses;

pulse rate converter means electrically connected to said conditionermeans for generating an analog DC potential having a voltageproportional to the frequency of said modulated electrical pulses;

comparator means electrically connected to said pulse rate converter forgenerating an electrical output signal when said DC potential is equalto or less than a reference DC potential corresponding to said selectedvehicle speed;

a gun adapted to fire an electrically detonable cartridge of colormarking substance responsive to the electrical output signal from saidcomparator means; and

means for mounting said gun in a vertical, downwardly directed positionso that said color marking substance is propelled downwardly againstsaid surface when said cartridge is detonated.

5. The device defined in claim 4 including means electrically connectedto said pulse rate converter for indicating and/or recording said analogDC potential.

lib

6. The device defined in claim 4 including means electrically connectedto said conditioner means and to said comparator means for totalizingthe number of modulated electrical pulses occurring during the periodthat said comparator means is generating said electrical output signal.

7. A device for marking on a surface the location where a vehicletraveling over the surface attains a selected speed, which comprises:

a wheel assembly adapted for attachment to said vehicle, said assemblycomprising a frame, an axle connected to said frame, a wheel rotatablymounted on said axle and adapted for rolling contact with said surface,and an opaque disc mounted so as to rotate with said wheel, said dischaving a plurality of light pervious areas of uniform size and shapeevenly disposed around its periphery and substantially equidistantfromthe axis of said wheel;

a light source mounted at one side of said disc adjacent to said lightpervious area;

a photoelectric cell mounted on the opposite side of said disc from saidlight source and aligned so that light from said light source passesthrough said light pervious area and impinges on said photoelectric cellthereby causing said photoelectric cell to generate an electricalimpulse;

conditioner means electrically connected to said photoelectric cell forreceiving said electrical impulses and generating a modulated electricalimpulse for each electrical impulse received from said photoelectriccell;

pulse rate converter means electrically connected to said conditionermeans for receiving said modulated impulses and generating an analog DC.potential having a voltage proportional to the rate at which saidmodulated impulses are received;

comparator means electrically connected to said pulse rate converter forreceiving said analog DC potential and producing an electrical outputsignal when said analog DC potential is equal to or less than areference DC potential corresponding to said selected vehicle speed;

a gun adapted for attachment to said frame for firing an electricallydetonable cartridge containing a color marking substance downwardlyagainst said surface; and

detonating means electrically connected to said comparator means and tosaid cartridge for producing an electrical detonating signal responsiveto said electrical output signal.

8. The device defined in claim 7 wherein said detonating means includesa first switching means that is rendered conductive by said electricaloutput signal.

9. The device defined in claim 8 wherein said vehicle is equipped withbrakes and wherein said detonating means includes a second switchingmeans that is closed when said brakes are applied.

10. A device for measuring the distance traversed by a vehicle'travelingover a surface, which comprises:

a wheel assembly adapted for attachment to said vehicle, said assemblycomprising a frame, an axle connected to said frame, a wheel rotatablymounted in said axle and adapted for rolling contact with said surface,and an opaque disc mounted so as to rotate with said wheel, said dischaving a plurality of light pervious areas of uniform size and shapeevenly disposed around its periphery and substantially equidistant fromthe axis of said wheel;

a light source mounted on said frame at one side of said disc adjacentto said light pervious area;

a photoelectric cell mounted on said frame on the opposite side of saiddisc from said light source and aligned so that light from said lightsource passes through said light pervious areas and impinges on saidphotoelectric cell thereby causing said photoelectric cell to generatean electrical impulse;

conditioner means electrically connected to said photoelectric cell forreceiving said electrical impulses and generating a modulated electricalimpulse for each electrical impulse received from said photoelectricalcell;

pulse rate converter means electrically connected to said conditionermeans for receiving said modulated impulses and generating an analog DCpotential having a voltage proportional to the rate at which saidmodulated impulses are received;

comparator means electrically connected to said pulse rate converter forreceiving said analog DC potential and producing an electrical outputsignal when said analog DC potential is equal to or less than areference DC potential corresponding to said selected vehicle speed;

a pulse counter electrically connected to said conditioner means througha first switching means responsive to said electrical output signal.

1. A device for marking on a surface the location where a vehicletraveling over the surface attains a selected speed, which comprises:speedometer means adapted for attachment to said vehicle for generatingan electrical signal proportional to the speed of said vehicle; a gunadapted to fire an electrically detonable cartridge containing a colormarking substance, said gun being adapted for mounting in a vertical,downwardly directed position above said surface; and means electricallyconnected to said cartridge for detonating said cartridge when thegenerated electrical signal attains a value corresponding to theselected speed; whereby, upon detonation of the cartridge, the colormarking substance is propelled downwardly against said surface to markthereon the location that the vehicle attains the selected speed.
 2. Thedevice defined in claim 1 wherein the electrical signal generated bysaid speedometer means is a relatively non-oscillating DC potentialhaving a voltage proportional to the speed of the vehicle.
 3. A devicefor marking on a surface the location where a vehicle traveling over thesurface attains a selected speed, which comprises: a frame adapted fordetachable connection to said vehicle; a wheel rotatably mounted on saidframe and adapted for rolling contact with said surface; speedometermeans for generating an electrical signal proportional to the speed ofrevolution of said wheel; a gun adapted to fire an electricallydetonable cartridge containing a color marking substance, said gun beingmounted in a vertical, downwardly directed position on said frame; andmeans electrically connected to said cartridge for detonating saidcartridge when the generated electrical signal attains a valuecorresponding to the selected speed.
 4. A device for marking on asurface the location where a vehicle traveling over the surface attainsa selected speed, which comprises: speedometer means adapted forattachment to said vehicle for generating a series of electrical pulseshaving a frequency proportional to the speed of said vehicle;conditioner means electrically connected to said speedometer means formodulating said electrical pulses so as to produce a series of modulatedelectrical pulses; pulse rate converter means electrically connected tosaid conditioner means for generating an analog DC potential having avoltage proportional to the frequency of said modulated electricalpulses; comparator means electrically connected to said pulse rateconverter for generating an electrical output signal when said DCpotential is equal to or less than a reference DC potentialcorresponding to said selected vehicle speed; a gun adapted to fire anelectrically detonable cartridge of color marking substance responsiveto the electrical output signal from said comparator means; and meansfor mounting said gun in a vertical, downwardly directed position sothat said color marking substance is propElled downwardly against saidsurface when said cartridge is detonated.
 5. The device defined in claim4 including means electrically connected to said pulse rate converterfor indicating and/or recording said analog DC potential.
 6. The devicedefined in claim 4 including means electrically connected to saidconditioner means and to said comparator means for totalizing the numberof modulated electrical pulses occurring during the period that saidcomparator means is generating said electrical output signal.
 7. Adevice for marking on a surface the location where a vehicle travelingover the surface attains a selected speed, which comprises: a wheelassembly adapted for attachment to said vehicle, said assemblycomprising a frame, an axle connected to said frame, a wheel rotatablymounted on said axle and adapted for rolling contact with said surface,and an opaque disc mounted so as to rotate with said wheel, said dischaving a plurality of light pervious areas of uniform size and shapeevenly disposed around its periphery and substantially equidistant fromthe axis of said wheel; a light source mounted at one side of said discadjacent to said light pervious area; a photoelectric cell mounted onthe opposite side of said disc from said light source and aligned sothat light from said light source passes through said light perviousarea and impinges on said photoelectric cell thereby causing saidphotoelectric cell to generate an electrical impulse; conditioner meanselectrically connected to said photoelectric cell for receiving saidelectrical impulses and generating a modulated electrical impulse foreach electrical impulse received from said photoelectric cell; pulserate converter means electrically connected to said conditioner meansfor receiving said modulated impulses and generating an analog D.C.potential having a voltage proportional to the rate at which saidmodulated impulses are received; comparator means electrically connectedto said pulse rate converter for receiving said analog DC potential andproducing an electrical output signal when said analog DC potential isequal to or less than a reference DC potential corresponding to saidselected vehicle speed; a gun adapted for attachment to said frame forfiring an electrically detonable cartridge containing a color markingsubstance downwardly against said surface; and detonating meanselectrically connected to said comparator means and to said cartridgefor producing an electrical detonating signal responsive to saidelectrical output signal.
 8. The device defined in claim 7 wherein saiddetonating means includes a first switching means that is renderedconductive by said electrical output signal.
 9. The device defined inclaim 8 wherein said vehicle is equipped with brakes and wherein saiddetonating means includes a second switching means that is closed whensaid brakes are applied.
 10. A device for measuring the distancetraversed by a vehicle traveling over a surface, which comprises: awheel assembly adapted for attachment to said vehicle, said assemblycomprising a frame, an axle connected to said frame, a wheel rotatablymounted in said axle and adapted for rolling contact with said surface,and an opaque disc mounted so as to rotate with said wheel, said dischaving a plurality of light pervious areas of uniform size and shapeevenly disposed around its periphery and substantially equidistant fromthe axis of said wheel; a light source mounted on said frame at one sideof said disc adjacent to said light pervious area; a photoelectric cellmounted on said frame on the opposite side of said disc from said lightsource and aligned so that light from said light source passes throughsaid light pervious areas and impinges on said photoelectric cellthereby causing said photoelectric cell to generate an electricalimpulse; conditioner means electrically connected to said photoelectriccell for receiving said electricAl impulses and generating a modulatedelectrical impulse for each electrical impulse received from saidphotoelectrical cell; pulse rate converter means electrically connectedto said conditioner means for receiving said modulated impulses andgenerating an analog DC potential having a voltage proportional to therate at which said modulated impulses are received; comparator meanselectrically connected to said pulse rate converter for receiving saidanalog DC potential and producing an electrical output signal when saidanalog DC potential is equal to or less than a reference DC potentialcorresponding to said selected vehicle speed; a pulse counterelectrically connected to said conditioner means through a firstswitching means responsive to said electrical output signal.